JPH01269595A - Plate surface protective agent for planographic plate - Google Patents

Abstract

PURPOSE:To enable a reduction in the amount of spoilage, even in the case of rotary offset printing or other printing in which ink removal property is poor in the beginning of printing, by using a plate surface protective agent for a planographic plate comprising an aqueous solution containing a starch modified by phosphoric acid or a derivative thereof and having a film forming property and a specified amount of a surfactant. CONSTITUTION:A plate surface protective agent comprises an aqueous solution containing a starch modified by phosphoric acid or a derivative thereof and having a film-forming property and a specified amount of a surfactant, the specified amount being more than 10wt.% based on the total weight of the protective agent. The modified starch is obtained by bringing a starch into reaction with phosphorus oxychloride, a trimetaphosphoric acid salt, an orthophosphoric acid salt, a polyphosphoric acid salt, phosphoric acid, an organic phosphonic acid or the like to form a phosphoric acid ester. The surfactant, which must be contained in the protective agent as one of effective components of the agent, may be an anionic, nonionic, ampholytic or cationic surfactant or the like. The amount of the surfactant is preferably 10-25wt.% based on the protective agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a plate surface protective agent for lithographic printing plates.

[Conventional technology]

When making a lithographic printing plate, in the final step, a plate surface protectant (so-called gum liquid) is applied to protect the non-image area and the image area. This process is called gumming.

The purpose of gumming is not only to protect the hydrophilicity of the non-image area, but also to make corrections such as adding or erasing the image area, to preserve it after plate making until printing or to preserve it until reuse, and to protect it when installing it on a printing machine. The objective is to protect printing plates from stains and scratches caused by adhesion of fingerprints, oil, fat, dust, etc. during handling, and to suppress the occurrence of oxidation stains. Conventionally, gum liquid compositions used as plate surface protectants for lithographic printing plates are usually made of gum arabic, cellulose gum, or an aqueous solution of a water-soluble polymeric substance having a carboxyl group in the molecule. It also contains pH adjusters, preservatives, etc. as necessary.

Gumming methods include pouring a gum solution onto the plate, spreading it over the entire plate surface with a sponge or cotton tampon, and rubbing it with a wiping cloth until the plate surface is dry; an automatic gum application process that is carried out after development and washing; Examples include an automatic gumming process that is performed immediately without washing the developing machine with water, and an automatic gumming process that is performed after development with a rinsing solution containing a surfactant.

The printing plate made in this way is attached to a printing machine and printed according to the following procedure.

Sheet-fed printing is a method in which the gum on the plate surface is removed with a water rod such as a Molton roll at the time of printing, and then an ink roll is applied to the plate surface for printing. (Waste paper refers to printed matter that has no commercial value, such as printed matter where the ink density in the image area is low or the non-image area is dirty.)

However, when printing begins, an ink roll is attached to the printing plate, ink is applied to the entire printing plate, and immediately after that, a water rod is applied to the printing plate.
In the case of printing methods such as off-wheel printing, in which printing is performed by removing ink from the plate surface, conventionally known gum liquids have poor ink removability because the ink adheres to the gum in the non-image area. There is a problem in that there is a very bad problem in that there is a large amount of waste paper with dirty non-image areas.

Various methods have been tried to reduce the amount of paper wasted due to this phenomenon, which would result in significant cost reductions.

For example, methods are being considered that include removing gum with a sponge or the like before printing starts, or supplying more water to the printing plate at the start of printing than during normal printing to make it easier to remove gum. However, these methods are undesirable because they complicate the work, reduce workability, and cause troubles due to paper breakage.

[Problem to be solved by the invention]

Therefore, an object of the present invention is to provide a plate surface protectant that can reduce paper waste even in printing methods such as off-wheel printing that have poor ink removability at the beginning of printing.

Still another object of the present invention is to provide a good plate surface protectant for lithographic printing plates that will not be scratched or smeared with fingerprints during handling during the period from plate making to printing. A further object of the present invention is to provide a plate surface protectant that causes less staining on the blanket during printing and also causes less printing stains when printing is resumed after the printing press has stopped.

As a result of intensive research to achieve the above objective, the present inventors have
This is what led to the present invention.

[Means to solve the problem]

The object of the present invention is to provide a lithographic printing process consisting of an aqueous solution containing a starch having film-forming properties modified with phosphoric acid or its derivatives and a surfactant in an amount of more than 10% by weight based on the total weight of the plate surface protective agent. This can be achieved by using a plate surface protectant.

The plate surface protective agent in the present invention must contain, as one of its organic components, a starch modified with phosphoric acid or a derivative thereof (hereinafter referred to as "modified starch"), which has film-forming properties.

The modified starch used in the present invention is obtained by reacting starch with phosphorus oxychloride, trimetaphosphate (e.g., sodium salt), orthophosphate, polyphosphate, phosphoric acid, organic phosphonic acid, etc. to form a phosphoric acid ester. It is something. Depending on the esterification agent, there are monoester type and crosslinked diester type, both of which can be used in the present invention, but monoester type is preferable because it causes less aging characteristic of starch. Raw material starches include potato, Japanese sweet potato, wheat, cupioca,
Starting with corn, glutinous corn, rice, and glutinous rice (
What is asked is used.

The substitution rate (esterification rate) of phosphorylated starch is theoretically possible up to a substitution rate of 3, in which all three hydroxyl groups of the glucose residues of starch are esterified, but the preferred range is a substitution rate of 0.
03 to 1.0, more preferably 041 to 0.6.

As mentioned above, the modified starch used in the present invention is one in which phosphoric acid or a phosphoric acid derivative is ester-bonded to the hydroxyl group of glucose constituting the starch, and is a polymer compound containing units represented by the following general formula. be.

In the above general formula, R1 to R3 may be the same or different and each represents a hydrogen atom, a phosphoric acid or a phosphoric acid derivative residue.

The synthesis method for the above modified starch is described in "Water-soluble polymers, water-dispersible resins general technical data collection" (Management Development Center Publishing Department)
(published on January 23, 1981, pages 68-69). Modified starch having desired properties can be obtained by variously selecting R1 to R3 in the above general formula.

The content of modified starch in the plate surface protective agent of the present invention is preferably 0.1% to 30% by weight, more preferably 0.3% to 30% by weight.
25% of duplicates. These modified starches are used as a homogeneous aqueous solution by dissolving them in water or by heating water (for example, 70 to 80°C) to dissolve them.

The plate surface protective agent in the present invention needs to contain a surfactant as one of the active ingredients. Surfactants that can be used include anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants.

For example, anionic surfactants include fatty acid salts, alkylbenzene sulfonates, linear alkylbenzene sulfonates, alkyl sulfates, α-olefin sulfonates, alkyl phosphate ester salts, dialkyl sulfosuccinate ester salts, and polyoxyethylene alkyl ethers. Sulfates, polyoxyethylene alkyl ether phosphates, alkylnaphthalene sulfonates,
Examples include N-lauroylsarcosine salts, sulfonates of naphthalene-formalin condensates, and diphenyl ether disulfonates. Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene polyoxypropylene block polymers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyethylene glycol fatty acid esters. There are polyoxyethylene fatty acid amines, fatty acid monoglycerides, sorbitan fatty acid esters, pentaerythritol fatty acid esters, sucrose fatty acid esters, amine oxides, etc.

Examples of amphoteric surfactants include alkylcarboxybetaine types, alkylaminocarboxylic acid types, and alkylimidacillin types. Examples of cationic surfactants include tetraalkylammonium salts, trialkylbenzylammonium salts, and alkylimidazolinium salts. Other examples include fluorine-based surfactants and silicone-based surfactants.

Among the surfactants, anionic surfactants and/or nonionic surfactants are particularly effective. Two or more of these surfactants can also be used in combination.

The amount used is not particularly limited, but the preferred range is 10 to 25% by weight of the plate surface protectant.

More preferably, it is 10 to 25% by weight.

When the surfactant content of the plate surface protectant is less than 0%, in printing methods such as off-wheel printing, ink removal is poor at the beginning of printing, resulting in a large amount of dirty waste paper in non-image areas. .

In the present invention, other hydrophilic polymer compounds,
A water-soluble resin and other modified starch may be mixed.

Examples of such hydrophilic polymer compounds include cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, and carboxymethylcellulose, roasted starch, enzyme-modified starch, alkylene oxide-modified starch, pregelatinized starch, dextrin, and dialdehyde starch. Examples include natural or semi-synthetic polymeric compounds such as starch derivatives, alginates, locust bean gum, strafukun, sterabic, and pullulan.

Also, polyvinyl alcohol, polyvinylpyrrolidone,
Synthetic polymer compounds such as polyacrylamide, polyvinyl methyl ether, polyethylene oxide, a copolymer of vinyl methyl ether and maleic anhydride, and a copolymer of vinyl acetate and maleic anhydride can also be used in combination. Furthermore, gum arabic can also be used.

The hydrophilic polymer compound contained in the protective agent is 0.1 to 30
% by weight, more preferably 0.3 to 25% by weight.

The combined amount of phosphoric acid-modified starch and other hydrophilic polymer compounds contained in the protective agent is preferably 1% or more by weight.

It is more advantageous to use the plate surface protectant of the present invention in an acidic range of pH 2 to 6. In order to adjust the pH to 2 to 6, mineral acids, organic acids, inorganic salts, or alkaline agents are generally added to the plate surface protectant. The amount added is 0.01~3%
It is. For example, mineral acids include nitric acid, sulfuric acid, phosphoric acid, and the like. Examples of organic acids include citric acid, acetic acid, oxalic acid, malonic acid, p-toluenesulfonic acid, tartaric acid, malic acid, lactic acid, levulinic acid, phytic acid, benzoic acid, butyric acid, maleic acid, picolinic acid, and organic phosphonic acid. It's winter. Inorganic salts include nitric acid, phosphoric acid, sulfuric acid, molybdic acid, acetic acid, polyphosphoric acid, boric acid, water-soluble alkali metal salts and ammonium salts thereof, such as sodium nitrate, potassium nitrate, ammonium nitrate, monosodium phosphate, Sodium phosphate, potassium phosphate, potassium phosphate, primary ammonium phosphate, secondary ammonium phosphate, sodium sulfate, potassium sulfate, ammonium sulfate, sodium molybdate, potassium molybdate, ammonium molybdate, Examples include sodium acetate, potassium acetate, ammonium acetate, sodium tripolyphosphate, sodium hexametaphosphate, sodium birophosphate, sodium borate, and ammonium borate.

Examples of the alkaline agent include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, and amines such as ammonia, monoethanolamine, jetanolamine, and triethanolamine. Two or more types of mineral acids, organic acids, inorganic salts, alkali agents, etc. may be used in combination.

In addition to the above components, lower alcohols such as glycerin, ethylene glycol, and triethylene glycol can also be used as wetting agents if necessary.

The amount of these wetting agents used is 0.1 to 5% by weight in the composition.
, more preferably 0.5 to 3% by weight. In addition to the above, benzoic acid and derivatives thereof, phenol, formalin, sodium dehydroacetate, and the like can be added as preservatives to the plate surface protectant of the present invention in a range of 0.005 to 2.0% by weight.

Furthermore, dyes, antifoaming agents, etc. can also be added.

The above plate protectant components are contained in water in a wide range of concentrations, but - for boat fishing, 4 to 40%, more preferably 5 to 30%.
used within the range. The plate surface protective agent of the present invention can be applied uniformly by spreading it over the entire plate surface with a sponge or the like and rubbing it with a wiping cloth until dry. In addition, the plate surface protective agent of the present invention can be used after developing a positive PS plate mainly composed of an 0-quinonediazide photosensitive material with an alkaline solution such as a silicate.
Alternatively, a normal negative PS plate using a condensate of p-diazodiphenylamine and roseformaldehyde as a photosensitive material can be used as an aqueous plate containing an anionic surfactant, an alkaline agent, a poorly water-soluble organic solvent such as benzyl alcohol or phenyl cellosolve, sulfite, etc. After developing with a developer, a positive PS plate and a negative PS plate are developed in common, and after developing with a developer having a similar mixed composition of the above two types of developers, an automatic coating method and a developing machine are carried out after washing with water. An automatic coating method that is performed without washing with water, an automatic coating method that is performed after processing with a rinse solution containing a surfactant after development, an automatic coating method that is performed after water circulation for pre-rinsing after development, and washing with water after pre-rinsing after development. The coating can be uniformly applied using an automatic coating method or the like that is carried out after the coating is applied.

〔Effect of the invention〕

By using the plate surface protectant of the present invention, even in printing methods such as off-wheel printing that generate a large amount of paper waste at the beginning of printing, the amount of paper waste can be reduced by 1 % compared to when conventional gum liquid is used. /2 to 173, and it is possible to obtain satisfactorily clear printed matter.

〔Example〕

This will be explained below using examples.

The plate surface protectants (A), (B), and (C) of the present invention having the following formulations were prepared.

Prescription of the plate protectant invented by Oki (Table 1) The pH was adjusted to 4.0 to 4.2 using phosphoric acid and potassium hydroxide.

For comparison, conventional plate protectants (D) and (
E) was created.

0 Conventional plate protectant formulation (Table 2) The pH was adjusted to 4.0 to 4.2 using phosphoric acid and potassium hydroxide.

The surface of a JIS 1050 aluminum sheet was grained using a rotating nylon brush using a pumice water suspension as an abrasive. The surface roughness (center line average roughness) at this time is 0.
It was 5μ. After washing with water, add 10% caustic soda solution to 70%
It was etched by immersing it in a solution warmed to ℃ so that the amount of aluminum dissolved was 6 g/m'. After washing with water, it was immersed in a 30% nitric acid aqueous solution for 1 minute to neutralize it, and then thoroughly washed with water. Thereafter, in a 0.7% nitric acid aqueous solution, a rectangular alternating waveform with an anode special voltage of 13 volts and a cathode special voltage of 6 volts was used (power supply waveform described in the example of JP-A-52-77702). Electrolytic surface treatment was performed for 20 seconds, and the surface was washed by immersion in a 20% sulfuric acid solution at 50°C, followed by water washing.

Create two grained boards as shown below, one of which weighs 150g/
Anodization treatment was carried out in a β sulfuric acid bath at a bath temperature of 40° C. and a flow rate of 5 A/dm' for 40 seconds, followed by thorough washing with water and drying. The weight of the anodic oxide film obtained was 2 g/m''. This support was designated as (A).

The other sheet was anodized in a 200 g/f phosphoric acid bath at a bath temperature of 40°C and 5 A/dm2 for 60 seconds, thoroughly washed with water, and then dried. The weight of the obtained anodic oxide film was 1.8 g/m'. This support was designated as (b).

Divide each of the supports in (a) and (b) into two, and (i)
, (E2), (Rho 1), and (Rho 2).

(E1) and (Rho1) were added to a 5% aqueous solution of potassium silicate (Sin2/0 molar ratio 2.0) kept at 70°C.
The sample was immersed for 0 to 60 seconds for hydrophilic treatment, thoroughly washed with water, and then dried.

2 on the aluminum support that has been subjected to the above hydrophilic treatment.
-Hydroquine ethyl methacrylate copolymer (synthesized by the method described in Example 1 of British Patent No. 1.505.739) 2.0 parts by weight, 2.0 parts by weight of a condensate of p-diazodiphenylamine and paraformaldehyde Methoxy-4-
Hydroxy-5-benzoylbenzenesulfonate 0
．． 12 parts by weight, Oil Blue #603 (manufactured by Orient Chemical Industry ■) 0.03 parts by weight, 1 part by weight of 2-methoxyethanol
A photosensitive solution consisting of 1 part of 5-layer, 1 part of methanol, 580 parts by weight of ethylene chloride was applied to the supports of (E1) and (Row 1) so that the dry weight was 1.8 g/m', A photosensitive lithographic printing plate was obtained. This photosensitive lithographic printing plate was exposed to light using a halftone negative film, and 3.0 parts by weight of sodium sulfite, 30.0 parts by weight of benzyl alcohol, 20.0 parts by weight of triethanolamine, and 5.0 parts by weight of monoethanolamine were prepared. , 10.0 parts by weight of sodium t-butylnaphthalenesulfonate and 1000 parts by weight of pure water, followed by washing with water and drying.

On the other hand, polyhydroxyphenyl naphthoquinone-1,2-diazide-5 obtained by condensation polymerization of acetone and pyrogallol is described in Japanese Patent Publication No. 43-28403.
- A photosensitive solution was prepared by dissolving sulfonic acid ester 1 heavy II and 2 parts by weight of novolac type cresol formaldehyde resin in 40 parts by weight of methyl cellosolve, and the dry weight of 2. A photosensitive lithographic printing plate was obtained by coating at a coating weight of 0 g/m'. This photosensitive lithographic printing plate was exposed to light using a halftone positive film, and 3%
The film was developed with an aqueous sodium silicate solution, washed with water, and dried.

Above (E1), (E2), (Rho 1), (Rho 2)
The plate surface protectants (Δ) to (E) were applied uniformly to each of the printing plates using an automatic gumming machine at a coating density of 0.2 to 0.5 g/m', and then heated at a temperature of 50 to 60°C. It was dried for 30 to -5 seconds.

After 30 minutes, ink each plate (Toyo Ink 1)
Using Shusei Web King Sumi) and dampening water (EU-3100 times diluted solution manufactured by Fuji Photo Film @), Shinetsu Pulp's paper was printed using a Komori Printing Machine's off-wheel printing machine (model system 18LR-418). Printed using rough paper.

Table 3 shows the number of sheets of waste paper until a clear printed matter with sufficient ink removed was obtained.

0 Printing evaluation results (number of sheets of waste paper at the start of printing) (Table 3) As is clear from this example, the amount of paper waste at the start of printing when the lithographic printing plate using the plate surface protectant of the present invention was subjected to off-wheel printing. It can be seen that the amount is extremely small compared to when a conventional plate surface protectant is used.

Claims (1)

[Claims] A lithographic printing plate comprising an aqueous solution containing film-forming starch modified with phosphoric acid or a derivative thereof and a surfactant in an amount of more than 10% by weight based on the total weight of the plate surface protective agent. plate surface protectant.